Conventionally, more base stations have been established for increasing the number of usable wireless channels in an area when a wireless communication system in operation in this area has run short of usable wireless channels. To establish more base stations, there is a technology for connecting the base stations in cascade and allowing a master base station, which is one of the base stations, to control the call processing of the other of the base stations (see, for example, Japanese Unexamined Patent Application Publication No. 2004-180056).